Conan O’Brien was on the The Howard Stern Show earlier this week, where he told an entertaining anecdote about the “Marge vs. the Monorail” episode of The Simpsons, and the twist of fate that ended up with Leonard Nimoy making his now iconic cameo. Given Nimoy’s sad and untimely passing, I thought it would be a nice story to share and hopefully give people a smile.

See, Leonard Nimoy wasn’t the former Star Trek cast member Conan, who wrote the episode, had originally intended for the role. Long before he was a talk show host or even a writer on The Simpsons, Conan used to do a fake talk show out of his apartment, and he loved doing impersonations of George Takei. That stuck with him through the years, so when he was writing the “Monorail” episode, he wrote in a special cameo for Takei.

Takei turned it down, however, which absolutely crushed Conan. He eventually and somewhat hilariously found out later that the reason was because Takei was on the board of transportation in San Francisco, and he felt that the script “mocked the monorail, which is a valid form of transportation.” HIS ACTUAL REASON.

So, what were they to do? On a long shot, Al Jean thought to give Leonard Nimoy a call — who Conan correctly reasons is better, as he outranks Sulu — and Nimoy was more than happy to do it. And that was how Simpsons history was made. To this day, his appearance marks one of the best and most famous Simpsons cameos of all time, which he repeated four years later with “The Springfield Files.”

The whole segment is a solid listen, but the Takei-Nimoy story starts at about the 3:20 mark.